Kengo Master of Bushido - I played Bushido Blade 1 and 2 almost nonstop with my friends. Wanting a PS2 Bushido Blade was the reason I wanted a PS2. Kengo was hyped up as a spiritual successor, but it happened to lack any fun whatsoever. It took only one round of one match to figure that out. This one stung as I paid far more than the others.
The Void - One minute in, gameplay seemed cryptic and not too fun, but I hoped it might get better. Twenty minutes later, my initial reaction was proven correct. This was one of my first Steam sale purchases, and I really don't remember what compelled me to buy it.
Flotilla - This one looked neat, but it was also an early steam purchase. I don't really remember why I didn't like it, but it shows only 6 minutes played on steam.
Binding of Isaac and A Robot Named Fight - clearly lots of people enjoy both of these games, but I was already on the verge of puking from the artstyle before I could even control my characters. I gave each a few tries, but I soon erased each from my system. I think I got Isaac in a humble bundle, but I was already on the fence about it. I was psyched for Fight, but waited for a sale and even then regretted my purchase.